The present application relates generally to the non-invasive measurement of various substances in a body, such as the measurement of the concentration of glucose in the human body and, more specifically, to a far infrared detection system to analyze and determine, non-invasively, the concentration of a substance in a body.
Spectroscopic techniques using infrared (“IR”) radiation are known in the prior art and have been widely used for non-invasive measurement of the concentration of substances of interest in a body. One area of particular interest is the use of these techniques for the non-invasive measurement of the concentration of glucose and other constituents of the human bloodstream.
The infrared spectra includes the near infrared (approximately 1 to 3 microns), the middle infrared (approximately 3 to 6 microns), the far infrared (approximately 6 to 15 microns), and the extreme infrared (approximately 15 to 100 microns). Typical prior art glucose and other non-invasive blood constituent measuring devices operate in the near infrared regions where the absorption of infrared energy by glucose and other blood constituents is relatively low. However, it is known that glucose and other blood constituents have strong and distinguishable absorption spectra in both the middle and far infrared regions.
It has been found in a far infrared detection system that the resolution of the system should be equivalent to 0.01° C. to provide sufficiently accurate measurements. At this high level of accuracy, the blackbody emission of any component of the system (mirrors, filters, field limiters, detector, for example) can cause perturbations in the measurement. The conventional solution to such a problem is to cool the system to a cryogenic temperature (−180° C., for example), and have the system sealed and filled with dry nitrogen to avoid moisture accumulation. However, for a consumer product, such a solution is impractical and expensive.